Thermodynamic reciprocating machine comprising a compressor

ABSTRACT

A thermodynamic reciprocating machine having an integral compressor in which at least one compression element is present within the buffer space and is connected to the pistonlike member which bounds the buffer space or to the associated piston rod, which element can vary the volume of a compression space, at least one piston ring being present as an inlet valve between the cooperating wall parts of the compression element and the compression space, said ring being incorporated in a groove in the wall of the compression element or of the compression space, an open communication being always present between the compression space and the space in the groove behind the piston ring, the outlet valve which communicates with the compression space being accomodated in the wall of the compression space, the outlet being passed to the outside through a wall of the buffer space.

United States Patent Abrahams [4 Feb. 26, 1974 Primary ExaminerEdgar W.Geoghegan Assistant ExaminerH. Burks, Sr.

[75] Inventor: Ja-cobus. Abrahams Attorney, Agent, or Firm-Frank R.Trifari Emmasmgel, Emdhoven, Netherlands [7 3] Assignee: U.S. PhillipsCorporation, New

York, NY. [57] ABSTRACT [22] Filed: 1972 A thermodynamic reciprocatingmachine having an [21] Appl. No.: 246,141 integral compressor in whichat least one compression element is present within the buffer space andis connected to the pistonlike member which bounds the [30] ForegnApphcanon Prlomy Data buffer space or to the associated piston rod,which ele- May 4, 1971 Netherlands 7106039 ment can vary the volume of acompression Space at least one piston ring being present as an inletvalve be- [52] U.S. Cl. 60/521 tween the cooperating wan pans of thecompression III. CI. element and h compression p Said g b g [58] Fleldof Search incorporated in a groove i the wall of the p sion element orof the compression space, an open [56] References C'ted communicationbeing always present between the UNITED STATES PATENTS compression spaceand the space in the groove behind 2,558,495 6/ 1951 Muller et al. 60/24the pi n ring, the outlet valve which communicates 2,607,190 8/1952Kohler 60/24 with the compression space being accomodated in the2,616,243 /1952 n eenen 60/2 wall of the compression space, the outletbeing passed 3,550,371 12/1970 Jaspers 60/24 to the Outside through awall f the b ff space 3,667,348 6/l972 Gregorius 60/24 FOREIGN PATENTSOR APPLICATIONS 5 Claims, 4 Drawing Figures 655,565 7/l95l Great Britain60/24 21 17 i 17 20 1 20 22 15 7 E i I I l 1 I Q THERMODYNAMICRECIPROCA'I'ING MACHINE COMPRISING A COMPRESSOR The invention relates toa thermodynamic reciprocating machine comprising a working space inwhich a medium performs a thermodynamic cycle and the volume of whichcan be varied by pistons which can reciprocate with a mutual phasedifference, one surface of at least one piston influencing the volume ofthe working space and the other surface influencing the volume of abuffer space in which an average medium pressure prevails which is atleast substantially equal to the average medium pressure in the workingspace, said piston being connected to a driving mechanism via a pistonrod passed through a wall of the buffer space, the machine comprising acompressor for forcing medium from the said spaces into a high pressuremedium storage container, said compressor comprising an inlet valvewhich communicates with the buffer space as well as an outlet valvewhich can be made to communicate-with the storage container via anoutlet.

A thermodynamic reciprocating machine of this type is known from the USPat. No. 3,372,539. In this case the compressor forms part of a powercontrol device. For controlling the power of the machine, the averagemedium pressure level in the working space of the machine is varied bywithdrawing and supplying, respectively, medium from and to,respectively, said space. When medium is withdrawn, said medium isforced into a high pressure storage container by the compressor.

As a result of the presence of the medium-filled buffer space the largepressure forces exerted by the medium in the working space on the pistonare compensated for; the rod forces in the driving mechanism arecomparatively small so that said driving mechanism may have acomparatively light construction, also a low pressure can prevailin thecrankcase, so that the construction of the walls of said case can alsobe comparatively light.

Thermodynamic reciprocating machines are to be understood to includewithin the scope of the present invention, hot gas reciprocatingengines, cold-gas reciprocating machines and heat pumps. In the workingspace of such machines, the medium is alternately compressed when it ismainly present in a partial space of the working space, the compressionspace, then transported to a partial space, the expansion space, via aregenerator; subsequently, when the medium is mainly present in theexpansion space, it is expanded and finally transported back to thecompression space again via the regenerator, after which the cycle iscompleted. The compression and expansion spaces have differenttemperatures during operation. Structurally, such thermodynamicreciprocating machines are to be divided into thermodynamicreciprocating machines of the displacer type (British Pat. No.1,024,274) and thermodynamic reciprocating machines of the two pistontype (British Pat. No. 1,053,896). In thermodynamic reciprocatingmachines of the displacer type, a piston ensures the alternatecompression and expansion of the medium in the working space, while adisplacer ensures the transport of the medium from the compression spaceto the expansion space and vice versa. The displacer may be connected toa driving mechanism, or not be coupled mechanically and be reciprocatedas a free displacer by medium pressure forces.

In thermodynamic reciprocating machines of the two-piston type, both acompression piston and an expansion piston are present which incooperation ensure the desirable compression, the transport and theexpansion of the mecium.

In the thermodynamic reciprocating machine known from the US. Pat. No.3,372,539, the compressor is present separately as a part of the powercontrol. This exhibits a few drawbacks. First of all, as a result ofthis the assembly of thermodynamic reciprocating machine with powercontrol device is rather bulky. This is a drawback in particular forapplications in which the available space is minimum, for example, incases in which the thermodynamic reciprocating machine isa hot gasengine applied as a power source in vehicles, aircraft, submarines or incases of cold gas refrigerators used on board, for example, aircraft.Special precautions are necessary for driving the compressor in the caseof hot gas engines a separate driving mechanism outside the engine and aspecial coupling to a shaft of the engine, respectively; in cold gasrefrigerators, in which an electric motor is usually accommodated in thecrank-case of the engine as a drive, a separate driving mechanism.

Conventional compressors furthermore exhibit the drawback that someleakage of lubricating oil usually occurs from the sump to the workingspace of the compressor. Said lubricating oil is dragged along bycompressed medium as a result of which pollution occurs in the system ofducts, the storage container, and the machine. In particular when oilreaches the regenerator of the machine, this has a disastrous effect onthe efficiency of the machine. Finally, the presence of the separatorcompressor having special driving precautions makes the plantcomparatively expensive.

It is the object of the present invention to provide a thermodynamicreciprocating machine in which the above-described drawbacks aremitigated. To achieve this object, the thermodynamic reciprocatingmachine according to the invention is characterized in that the mediumcompressor forms an integral part of the machine; at least onecompression element is present inside the buffer space and is connectedto the piston which bounds the buffer space or to the associated pistonrod, and this element can vary the volume of a compression space. Atleast one piston ring is present as an inlet valve between thecooperating wall parts of the compression element and the compressionspace. This ring is incorporated in a groove in the wall of thecompression element or of the compression space, with an opencommunication being always present between the compression space and thespace in the groove behind the piston ring. The outlet valve whichcommunicates with the compression space is accommodated in the wall ofthe compression space, the outlet being passed to the outside through awall of the buffer space.

Since the compressor now forms an integral part of the thermodynamicreciprocating machine, a compact and comparatively cheap assembly isobtained and a source of oil leak to the working medium is avoided.Structurally, all this is simple to provide, and a separate drivingmechanism of the compressor is no longer necessary. Since the inletvalve is constructed as a piston ring, the dead space normally inherentin inlet valves is minimum in the present case and a comparatively largecompression ratio of the integral compressor is obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 and 2 are cross-sectionalviews of hot gas engines of the displacer type FIGS. 3 and 4 arecross-sectional views of cold gas refrigerators of the two-piston type..

DESCRIPTION OF THE PREFERRED EMBODIMENT Reference numeral 1 in FIG. 1denotes a cylinder in which a piston 2 and a displacer 3 can reciprocatewith a mutual phase difference. The working face of the piston 2 variesthe volume of a working space which consists of two partial spaces, acompression space 4 present between the piston 2 and the displacer 3 andan expansion space 5 the volume of which is varied by the upper workingface of the displacer 3. The two spaces communicate with each other viaa cooler 6, a regenerator 7 and a heater 8.

The working space is filled with a medium, for example hydrogen orhelium, which performs a thermodynamic cycle in the working space.Thermal energy originating from a burner 9 can be supplied to saidmedium from without. With its lower surface, the piston 2 varies thevolume of a buffer space 10 present between the compression space 4 anda crankcase 11. The buffer space 10 is filled with the same medium ofthe same pressure as that of the working space, so that the pressureforces exerted on an average by the medium in the compression space 4 onthe working face of the piston 2 are substantially compensated for bythe average pressure forces exerted on the lower face of the piston 2 bythe medium in the buffer space 10.

Via the narrow gap 12 between the cylinder 1 and the piston 2, mediumcan flow from the compression space 4 to the buffer space 10 when thepressure level in the buffer space is reduced. The piston 2 isconnected, via a hollow piston rod 14 which is passed through the wall15 of the buffer space 10 in a gas-tight manner, to a driving mechanismwhich is not shown and is arranged inside the crankcase 11.

The displacer 3 is also connected to the driving mechanism via adisplacer rod 16 which is passed through the piston 2 and the hollowpiston rod 14 in a gas-tight manner. Inside buffer space 10 an annularplunger 17 is present as a compression element which is connected to thepiston rod 14 via a connection element 18. During the reciprocatingmovement of the piston rod 14, the annular plunger 17 varies the volumeof an annular compression space 19 which in this case is constituted bya recess in the wall 15 of the buffer space 10.

Between the cooperating wall parts of the plunger 17 and the compressionspace 19 are present two piston rings 20 and 21 which are incorporatedin grooves 22 and 23 in the outer and inner wall, respectively, of theplunger 17 and which serve as inlet valves for the compression space. Ontheir lower sides, the piston rings comprise radially extending grooves20 and 21, respectively, as a result of which there is always an opencommunication between the compression space 19 and the spaces in grooves22 and 23 behind the piston rings.

This open communication may also be realized differently, for example,by providing the grooves 22 and 23, instead of the piston rings 20 and21, on their lower surfaces with radially extending grooves or byproviding apertures in the plunger 17 which extend from the spaces inthe grooves behind the piston rings to the compression space 19. Thecompression space 19 comprises an outlet valve 24 which can be made tocommunicate with a storage container for high pressure medium (notshown) via an outlet 25 which is passed to the outside through the wallof the buffer space.

During operation of the hot-gas engine, the annular plunger 17 moveswith the piston rod 14 and the piston 2, respectively. When the plungermoves upwards, when the pressure in the compression space 19 is lowerthan in the buffer space 10, the sides of the piston rings 20 and 21comprising radial grooves engage the lower surfaces of the groove 22 and23 but together with these form no seals. Medium can be drawn from thebuffer space 10 into the compression space 19.

After plunger 17 has passed its uppermost position (top dead center) andmoves downwards, the upper sides of the piston rings 20 and 21 engagethe upper sides of the groves 22 and 23, when the pressure in thecompression space 19 becomes larger than in the buffer space 10, and agood seal is formed so that the medium present in the compression space19 cannot flow back to the buffer space 10.

The medium in the compression space 19 is then compressed and leavessaid space via outlet valve 24 which opens when the pressure in thecompression space 19 exceeds the pressure exerted by the output valvespring 24' and by the medium in the outlet 25.

When the power supplied by the engine is to be reduced, the medium isforced from the compression space 19 via outlet 25 into a high pressuremedium storage container. When maintaining a given engine power, themedium forced out of the engine by the plunger 17 can be returned via areturn duct directly to the buffer space 19 or the working space(compression space 4).

In FIG. 2 the same reference numerals are used as in FIG. 1 forcorresponding components but with suffix a added. In this embodiment,compression space 19a is bounded by piston rod 14a and a housing 30. Thevolume of compression space 19a is varied by a flange 31 of compressionelement 2a secured to piston rod 14a. Two piston rings 32 and 33 arepresent which again serve as an inlet valve. Piston ring 32 isincorporated in groove 34 in the wall of the flange 31, while pistonring 33 is accommodated in a groove 35 in the wall of the housing 30.The two piston rings 32 and 33 comprise radially extending grooves ontheir sides facing the compression space 19, which grooves again ensurethat there is always an open communication between the compression space19 and the space in the grooves 34 and 35 behind the piston rings 32 and33, respectively.

A rolling diaphragm 36 is present as a seal between the piston 14a andthe displacer rod 16a, said rolling diaphragm separating the workingspace from the crankcase 11a, while a rolling diaphragm 37 is presentbetween the housing 30 and the pistonrod 14a and separates the bufferspace 10a from the crankcase 11a. Medium can flow from the buffer space10 to the piston 33 via aperture 38 in the wall of the housing 30.

During the upward stroke of the piston rod 14a with a lower pressure incompression space 19a than in buffer space 10, the piston ring 32engages with its lower side having radial grooves the lower side of thegroove 34, while the piston ring 33 engages with its upper side providedwith radial grooves the upper surface of groove 35 so that medium canflow freely from the buffer space a via grooves 34 and 35 and pistonrings 32 and 33, respectively, to the compression space 19a. During thedownward stroke of the piston rod 14a, the medium in the compressionspace 19a is compressed by the flange 31. As soon as the pressure in thecompression space 190 is larger than in the buffer space 10a, the pistonring 31 engages with its upper side the upper surface of groove 34 and agood seal is obtained. In the same manner, piston rings 33 engages withits lower side the lower surface of the groove 35 and a good seal isproduced in this case also. Medium can no longer flow back to the bufferspace 10a and is further compressed until the outlet valve 34 opens.

The cold gas refrigerator shown in FIG. 3 comprises a cylinder 41 inwhich a compression piston 42 and an expansion piston 43 can reciprocatewith a mutual phase difference. Between the two pistons are arranged acooler 44, a regenerator 45 and a freezer 46 through which medium canflow from a compression space 47 to an expansion space 48 and viceversa. Two buffer spaces 49 and 50 are present in which an averagemedium pressure prevails which is equal to the average medium pressurein the working space.

Via a piston rod 51 which is passed to the exterior through wall 52 ofthe buffer space 50, piston 42 is connected to a driving mechanism notshown. A rolling diaphragm 53 is present as a seal between said wall andthe piston rod. The piston 42 comprises on its lower side two plungershaving plunger 55. The plungers can vary the volume of two compressionspaces 56 within two cylindrical sleeves 57 secured to the wall 52 ofthe buffer space 50. The two compression spaces 56 communicate with acommon duct which communicates with exhaust 60 via outlet valve 59.

Piston rings 62 are incorporated as inlet valves in grooves 61 in thewalls of the plungers 54. In this case also, the piston rings on theirsides facing the compression spaces type. comprise radially extendinggrooves. The operation of the integral compressor of the cold gasrefrigerator is equal to that of the hot gas engines shown in FIG. 1 and2, so that further description thereof is not deemed necessary.

In the cold-gas refrigerator shown in FIG. 4 the same reference numeralsare used for components corresponding to the refrigerator shown in FIG.3 but with suffix b.

In a manner analogous to the hot gas engine shown in FIG. 2, the pistonrod 51b in the present embodiment comprises a flange 61b which can varythe volume of compression space 62 within the housing 63. In this casealso, two piston rings 64 and 65 are present as inlet valves, pistonring 64 being incorporated in a groove in the wall of the flange 61b andpiston ring 65 being accommodated in a groove in the wall of the housing63.

Piston ring 64 comprises radially extending grooves on its lower sideand piston ring 65 comprises said grooves on its upper side. Medium canflow from the buffer space 50b to the piston ring 65 via aperture 66 inthe wall of the housing 63. For the rest, the operation of this integralcompressor is equal to that shown in F IG. 2, so that descriptionthereof is not deemed necessary.

Of course, all kinds of other embodiments of the integral compressor arepossible. At the same time, in the cold-gas refrigerators shown in FIG.3 and 4, an integral compressor may also be incorporated in the bufferspace 49, if desirable.

In the embodiments shown, the integral compressor always draws mediumdirectly from the buffer space. It is of course also possible to causethe compressor to draw medium directly from the working space. This maybe effected, for example, by connecting a duct to the inlet side of thecompressor, which duct is connected to the working space.

What is claimed is:

1. In a thermodynamic apparatus including within a cylindrical bore of ahousing, reciprocally movable c0- axial compression and displacerpistons which define with the bore a variable volume working space, anda variable volume buffer space adjacent one end of the compressionpiston, said spaces comprising a closed system in which a gas iscyclically compressed and expanded, with the average gas pressuresubstantially equal in the working and buffer spaces, the improvement incombination therewith of a compressor for forcing gas from said bufferspace out of said closed system, comprising a frame part of the housingwithin the buffer space defining a compression chamber including anscalable outlet, a compression element movable axially within saidchamber for varying the volume thereof, the chamber and element havingadjacent relatively moving wall surfaces between which is a spaceoperable as an inlet to said chamber, one of said adjacent surfaceshaving a groove therein, the groove having opposite top and bottom edgesrelative to said axis of the pistons, a sealing ring situated in saidgroove and having corresponding top and bottom edges, means for movingsaid compression element in phase with movement of said compressionpiston, the seal ring movable between first position with the top edgesof the ring and groove in contact in sealing relationship, and secondposition with the corresponding bottom edges in contact and a gaspassage defined therebetween whereby movement to said first positioncauses said ring to move until said bottom edges contact, and a volumeof said chamber is reduced, and gas therein is compressed and forcedthrough said outlet out of said system. i

2. Apparatus according to claim 1 operable with a gas storage container,further comprising means for communicating gas discharged from saidcompressor outlet to said container.

3. Apparatus according to claim 1 wherein said means for moving saidcompression piston and compression element compreses a single pistonrod, and wherein said compressor chamber and compressor element areannular and coaxial with said rod.

4. Apparatus according to claim 1 wherein said seal ring includes onsaid bottom edge a radial groove for providing said gas passage.

5. Apparatus according to claim 1 wherein the apparatus is a hot gasengine.

W105 UNITED STATES PATENT OFFICE 56 CERTIFICATE OF CORRECTION i mm 3,'93836 v I Dated Februery 2 1974 Inventor( s)' JACHOBUS HUBERTUSABRAHAMS It is certified that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

C01. 2, line 2 8, delete "Said" and insert --Suc Col. 5, line 3, "10"should be --l0a-- line 20, "34" should be -24- line45, after "spaces"delete "type" and insert Signed ahd sealed this 29th day of October1974.

(SEAL) Attest: I

McCOY M. GIBSON JR. 0. MARSHALL DANN Attesting Officer Commissioner ofPatents

1. In a thermodynamic apparatus including within a cylindrical bore of ahousing, reciprocally movable coaxial compression and displacer pistonswhich define with the bore a variable volume working space, and avariable volume buffer space adjacent one end of the compression piston,said spaces comprising a closed system in which a gas is cyclicallycompressed and expanded, with the average gas pressure substantiallyequal in the working and buffer spaces, the improvement in combinationtherewith of a compressor for forcing gas from said buffer space out ofsaid closed system, comprising a frame part of the housing within thebuffer space defining a compression chamber including an sealableoutlet, a compression element movable aXially within said chamber forvarying the volume thereof, the chamber and element having adjacentrelatively moving wall surfaces between which is a space operable as aninlet to said chamber, one of said adjacent surfaces having a groovetherein, the groove having opposite top and bottom edges relative tosaid axis of the pistons, a sealing ring situated in said groove andhaving corresponding top and bottom edges, means for moving saidcompression element in phase with movement of said compression piston,the seal ring movable between first position with the top edges of thering and groove in contact in sealing relationship, and second positionwith the corresponding bottom edges in contact and a gas passage definedtherebetween whereby movement to said first position causes said ring tomove until said bottom edges contact, and a volume of said chamber isreduced, and gas therein is compressed and forced through said outletout of said system.
 2. Apparatus according to claim 1 operable with agas storage container, further comprising means for communicating gasdischarged from said compressor outlet to said container.
 3. Apparatusaccording to claim 1 wherein said means for moving said compressionpiston and compression element compreses a single piston rod, andwherein said compressor chamber and compressor element are annular andcoaxial with said rod.
 4. Apparatus according to claim 1 wherein saidseal ring includes on said bottom edge a radial groove for providingsaid gas passage.
 5. Apparatus according to claim 1 wherein theapparatus is a hot gas engine.